141 lines
6.0 KiB
Plaintext
141 lines
6.0 KiB
Plaintext
VoxWare v3.0
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------------
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All features of v2.90-2 should work as earlier. There could be some
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omissions but they are unintentional. I started this version thread
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after v2.3 so all features implemented before it are there.
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New features
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============
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There are now two new device interfaces. The /dev/midi## is a raw
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tty like interface to MIDI ports. There is a device file for each MIDI
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port on your system. They are named (/dev/midi00 to /dev/midiNN).
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The second addition is the /dev/music which is higher level interface
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than the old /dev/sequencer. It's intended for writing device independent
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applications like sequencers.
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/dev/midi##
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-----------
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This interface should be usefull for applications like MIDI sysex librarians.
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There are (currently) no timing features so making music could be impossible.
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There are as many /dev/midi## devices as there are MIDI ports in the system.
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The /dev/midi00 is connected to the first one, /dev/midi01 to the second etc.
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These devices work like tty devices in raw mode. Everything written to them is
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sent out to the MIDI port. There is currently an extra delay of at most
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1/100th of sec but it will be removed later.
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The reading algorithm is little bit more complicated. There are two different
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cases:
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1) There is at least one byte in the input buffer.
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The read returns as many bytes as it can without waiting for more bytes.
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For example when a process reads 100 bytes and there are 10 bytes in the
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buffer, the read returns just 10 bytes.
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2) The input buffer is empty when the process calls read.
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The read waits for the first byte and then continues as in case 1. By
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default it waits infinitely but there is an ioctl for setting a timeout
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for this. The ioctl(fd, SNDCTL_MIDI_PRETIME, &time) changes the timeout.
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The time is given in 1/10th of seconds (10 means one second).
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Other ioctl calls:
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ioctl(fd, SNDCTL_MIDI_MPUMODE, &mode) is available for full MPU-401
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compatible devices such as MPU-IPC-T, MQ PC Midi Card or MQX-32.
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It's not available for the so called MPU UART ports of some soundcards
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(PAS16, SB16 etc). By default the MIDI port is in UART mode after open.
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If this ioctl is called with mode=1, the interface is put to the intelligent
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(coprocessor) mode. NOTE! The MIDI port will be reset when this ioctl is called.
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It could have some strange effects if not called immediately after open. This
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vall returns EINVAL if the midi port doesn't support the MPU-401 intelligent
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mode.
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ioctl(fd, SNDCTL_MIDI_MPUCMD, &cmdstruct) is valid only if the MIDI port
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is put to the coprocessor mode using ioctl(SNDCTL_MIDI_MPUMODE). It's used to
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send commands to a MPU-401 compatible MIDI cards. Please refer to the
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MPU-401 Technical Reference Manual (or Music Quest Technical Reference
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Manual) for descriptions of the commands.
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The argument of SNDCTL_MIDI_MPUCOMMAND is of type mpu_command_rec. It
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has the following fields:
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typedef struct {
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unsigned char cmd;
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char nr_args, nr_returns;
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unsigned char data[30];
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} mpu_command_rec;
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where:
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cmd Contains the command number.
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nr_args Number of arguments of the command.
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MUST BE INITIALIZED BEFORE CALL
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nr_returns Number of bytes returned by the command.
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MUST BE INITIALIZED BEFORE CALL
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data Buffer for the command arguments and returned
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data.
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Be extremely carefull with the nr_args and nr_returns fields. They
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must match the command. An incorrect value will put the card and
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the driver out of sync. Refer to the MPU-401/MQX-32M documentation for further
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datails.
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/dev/music (/dev/sequencer2)
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----------------------------
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This device file works much like the /dev/sequencer which has been present
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since the beginning. The main differences are the following:
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- /dev/sequencer makes the MIDI ports to look like the synth devices. In fact
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the result is somewhere between the MIDI specification and the synth devices of
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/dev/sequencer. Both kind of devices are accessed using the SEQ_START_NOTE()
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like macros. The voice number parameters of the API macros have been redefined
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to denote MIDI channels. This means that the driver allocates voices for
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the channels automaticly (this is a responsibility/right of an application
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with /dev/sequencer). The result is that a SEQ_START_NOTE() macro has
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similar effects for a synth channel than on a MIDI port. This kind of
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solution provides better device independence than the /dev/sequencer. The
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drawback is that the new interface doesn't permit so low level access to the
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device as the /dev/sequencer does. An application developer must choose between
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these two interfaces. I think the old /dev/sequencer is better for applications
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like module players while the new one is better for making generic sequencer
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programs.
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- There are no separate MIDI devices with the /dev/sequencer2. The
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ioctl(SNDCTL_SEQ_NRMIDIS) returns always zero. Instead the MIDI ports are
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shown as synth devices. ioctl(SNDCTL_SEQ_NRSYNTHS) on /dev/sequencer2 will
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return sum of internal synthesizers (GUS, OPL3) and MIDI ports in the systems.
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- The new interface is used much like the ordinary /dev/sequencer. The
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event format is new so you have to use the API macros defined in the
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sys/soundcard.h. The interface is will propably change before the final 3.0
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release but using the API macros should ensure compatibility in source level.
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The new event format is not recognized by version 2.X so don't try to
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distribute binaries compiled with soundcard.h of v3.X.
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- The basic API useage is similar to the current one. There are some new
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macros but the older ones should work as earlier. The most important
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incompatibility is that the /dev/sequencer2 driver allocates voices itself.
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The other one is that the application must send SEQ_START_TIMER() as its
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first event. Otherwise the timer is not started and the application waits
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infinitely.
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There are several new features but I don't document them here. There are
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some info in the soundcard.h (near the end). I have also included some
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sample code in the directory v30. Full documentation will
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appear in the Hacker's Guide later.
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Don't hesitate to contact me in case you have questions or comments.
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Hannu Savolainen
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hannu@voxware.pp.fi
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